Surgery through a trocar inserted cannula and particularly with an opening through the tissue of an animal or human abdominal wall has become an important means to minimize the extent of surgical invasion. The lessening of invasion improves the cosmetic result, shortens recovery and lowers the cost. Endoscopic internal surgical procedures and equipment are available and in use for a variety of medical operations including gall bladder, bowel and gynecological surgery. A proper and simple instrument to open the passage through the abdominal wall and provide a passage for surgical instruments such as laparoscopes, endoscopes and the like is needed.
U.S. Pat. No. 3,595,239 discloses a catheter tube having an obturator in the form of an electrode passing coaxially therethrough. The obturator electrode is connected to an electrosurgical generator in order to provide high frequency energy used to divide or cut tissue thereby forming a passage for the catheter coaxially about the obturator to pass therewith through the tissue. The tip of the obturator extends beyond the catheter tip and cuts the path for the over the obturator catheter. The catheter moves along with the obturator electrode by means of a ring disposed about the obturator proximal to the tip and inside the tip of the catheter. There is no disclosure of an electrosurgical tubular cutting element for opening a passage.
A copending application incorporated by reference and made a part of this disclosure is U.S. Ser. No. 7-823093, assigned to a common owner. The disclosure in that application has a means for sensing the impedance or load associated with the energy required to do the cutting during insertion of an obturator tip so that the energy may be automatically ceased when the load has changed meaningfully. That approach is useful with the electrosurgical tubular trocar disclosed herein because safe use of it may be augmented by the combination of the circuitry described therein with the trocar explained in this disclosure.
U.S. Pat. No. 4,232,676 has a knife blade which cuts and cauterizes the incision and in so doing self limits the current flow at the knife. Specifically, the flat scalpel like blade carries electrodes therewith. Across the electrodes current flows when there is a conductive path. After cutting the current cauterizes the incision sealing the wound and eliminating the current path. The cutting and coagulation are electrosurgical. A flat ceramic insulator supports the electrodes between which radio frequency current flows. The configuration and method for cutting and coagulation electrosurgically is bipolar so no teaching of monopolar cutting and coagulation exists. A monopolar tool and the dangers of changing loads realized upon reaching the inner cavity of the body remain unappreciated in the disclosure of U.S. Pat. No. 4,232,676.
U.S. Pat. Nos. 4,601,710 and 4,654,030 are incorporated herein by reference and made a part hereof. Those patents explain laparoscopic procedures with obturators in trocar tubes shielded by a sleeve. The obturators include sharpened tips that first pierce the tissue and carry the trocar coaxially thereabout into the body. The shielding sleeve may project beyond the sharpened tip thereby covering and guarding it after entry into the body cavity. Various automatic mechanical mechanisms are disclosed that activate the shield after penetration. No electrosurgical cutting is taught to lower the effort required of the surgeon to penetrate the body wall. Considerable physical force and subsequent control are needed to effectively place the trocar through the abdominal wall without accidentally puncturing the bowel or other internal organs. The shielding provided in recognition of the almost impossible dexterity required to make a proper penetration has not eliminated the excessive force needed to drive the sharpened tip inward. Trocars are typically between 5 and 10 millimeters in diameter and the unit loading, kilograms per square millimeter, although reduced by the sharpened tip is significant.
U.S. Pat. No. 4,535,773 discloses techniques for shielding the sharp tip of a trocar by either interposing an extensible shielding sleeve or retracting the trocar into its tube. With regard to the latter, a solenoid operated detent holds the trocar in an extended position relative its tube and electronic sensing in the tip of the trocar is used to activate the detent for release. Nothing in this reference has any disclosure of electrosurgical cutting with a tubular trocar with an impedance responsive circuit to regulate an electrosurgical generator, attached to an electrosurgical cutting tip. The sensors and switches are disclosed in conjunction with a probe which retracts during penetration. In particular, the probe extends beyond the cutting surface until the abdominal wall has been traversed. The sensors can be connected to an audible or visual signal to indicate completion of the puncture. The switches could be mechanical or magnetic, be tripped by a sleeve in the puncturing instrument, a probe or a spring wire protruding from the tip or blade of a sharp pointed cutter. Multiple sensors in the cutting probe and the cannula can be used to signal the penetration position.
U.S. Pat. No. 4,919,653 discloses a device for locating epidural space. The release of force on the tip of a needle triggers an alarm which activate a solenoid latch permitting the needle and its sleeve to move in a cannula in response to an activated electromagnet such that the distal end moves 2 mm into the epidural space. Pressure sensors detect when the depression or release of pressure occurs as the needle enters the epidural space. The pressure signal is converted to produce the voltage difference between the sensor and the potentiometer. This difference is shown on a meter. The pressure sensor can be a small membrane with electrical contacts which are closed in the unloaded position and open when the membrane moves when the epidural space is reached. The passage of current through the contacts keeps the circuit open by means of a relay.
To safely place a cannula by a trocar technique requires knowledge of the position of the distal cutting tip thereof. The cutting edge, tip, is used to open the passage for the cannula through the animal or human tissue of the abdominal wall. A device to eliminate the needed to instantly indicate when the cutting tip has passed through the tissue and reached the inside of the body is needed so that the internal organs are not injured. Because the organs fill the inside cavity and are close to the wall there is the possibility of injury before the surgeon can stop advancing the distal cutting tip. A lessening of the forced needed to penetrate will improve control and reduce the likelihood of accidental injury. This is particularly so wherein the control of the energy applied to the electrosurgery is regulated according to load.